Integrated circuit devices configured to control discharge of a control gate voltage

ABSTRACT

Integrated circuit devices include a first node, a second node, a transistor connected between the first node and the second node, a current path between a control gate of the transistor and the second node, and a controller configured to concurrently discharge a voltage level of the first node and a voltage level of the second node, monitor a representation of a voltage difference between the voltage level of the first node and a voltage level of the control gate of the transistor while discharging the voltage level of the first node and discharging the voltage level of the second node, activate the current path if the voltage difference is deemed to be greater than a first value, and deactivate the current path if the voltage difference is deemed to be less than a second value.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/866,982, filed Jan. 10, 2018, titled “CONTROLLING DISCHARGE OF ACONTROL GATE VOLTAGE,” and claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/610,972, filed Dec. 28, 2017 and titled,“CONTROLLING DISCHARGE OF A CONTROL GATE VOLTAGE,” which are commonlyassigned and incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to memory and, in particular,in one or more embodiments, the present disclosure relates to methods ofoperating memory for controlling discharge of a control gate voltage,e.g., during or following an erase operation.

BACKGROUND

Integrated circuit devices traverse a broad range of electronic devices.One particular type include memory devices, oftentimes referred tosimply as memory. Memory devices are typically provided as internal,semiconductor, integrated circuit devices in computers or otherelectronic devices. There are many different types of memory includingrandom-access memory (RAM), read only memory (ROM), dynamic randomaccess memory (DRAM), synchronous dynamic random access memory (SDRAM),and flash memory.

Flash memory has developed into a popular source of non-volatile memoryfor a wide range of electronic applications. Flash memory typically usea one-transistor memory cell that allows for high memory densities, highreliability, and low power consumption. Changes in threshold voltage(Vt) of the memory cells, through programming (which is often referredto as writing) of data storage structures (e.g., floating gates orcharge traps) or other physical phenomena (e.g., phase change orpolarization), determine the data state (e.g., data value) of eachmemory cell. Common uses for flash memory and other non-volatile memoryinclude personal computers, personal digital assistants (PDAs), digitalcameras, digital media players, digital recorders, games, appliances,vehicles, wireless devices, mobile telephones, and removable memorymodules, and the uses for non-volatile memory continue to expand.

A NAND flash memory is a common type of flash memory device, so calledfor the logical form in which the basic memory cell configuration isarranged. Typically, the array of memory cells for NAND flash memory isarranged such that the control gate of each memory cell of a row of thearray is connected together to form an access line, such as a word line.Columns of the array include strings (often termed NAND strings) ofmemory cells connected together in series between a pair of selectgates, e.g., a source select transistor and a drain select transistor.Each source select transistor may be connected to a source, while eachdrain select transistor may be connected to a data line, such as columnbit line. Variations using more than one select gate between a string ofmemory cells and the source, and/or between the string of memory cellsand the data line, are known.

In programming memory, memory cells may generally be programmed as whatare often termed single-level cells (SLC) or multiple-level cells (MLC).SLC may use a single memory cell to represent one digit (e.g., bit) ofdata. For example, in SLC, a Vt of 2.5V might indicate a programmedmemory cell (e.g., representing a logical 0) while a Vt of −0.5V mightindicate an erased cell (e.g., representing a logical 1). An MLC usesmore than two Vt ranges, where each Vt range indicates a different datastate. Multiple-level cells can take advantage of the analog nature of atraditional charge storage cell by assigning a bit pattern to a specificVt range. While MLC typically uses a memory cell to represent one datastate of a binary number of data states (e.g., 4, 8, 16, . . . ), amemory cell operated as MLC may be used to represent a non-binary numberof data states. For example, where the MLC uses three Vt ranges, twomemory cells might be used to collectively represent one of eight datastates.

In erasing memory, memory cells might be erased by grounding accesslines of a block of memory cells while applying a relatively high erasevoltage (e.g., about 20V or more) to a source and data lines of theblock of memory cells, and thus to the channels of those memory cells,to remove charge from their data storage structures. Although voltagelevels of an erase operation may be well controlled as voltages areapplied, their discharge may be less controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a memory in communication with aprocessor as part of an electronic system, according to an embodiment.

FIGS. 2A-2B are schematics of portions of an array of memory cells ascould be used in a memory of the type described with reference to FIG.1.

FIG. 3 is a schematic illustrating circuitry for selective connection ofa data line, for an array of memory cells as could be used in a memoryof the type described with reference to FIG. 1, to a source or othercircuitry of the memory.

FIG. 4 is a block schematic of circuitry for selectively controllingdischarge of a control gate voltage in accordance with an embodiment.

FIG. 5 is a timing diagram for use in describing operation of thecircuitry of FIG. 4 in accordance with an embodiment.

FIG. 6 is a flowchart of a method of operating a memory in accordancewith an embodiment.

FIG. 7 is a flowchart of a method of operating a memory in accordancewith an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown, byway of illustration, specific embodiments. In the drawings, likereference numerals describe substantially similar components throughoutthe several views. Other embodiments may be utilized and structural,logical and electrical changes may be made without departing from thescope of the present disclosure. The following detailed description is,therefore, not to be taken in a limiting sense.

The term “semiconductor” used herein can refer to, for example, a layerof material, a wafer, or a substrate, and includes any basesemiconductor structure. “Semiconductor” is to be understood asincluding silicon-on-sapphire (SOS) technology, silicon-on-insulator(SOI) technology, thin film transistor (TFT) technology, doped andundoped semiconductors, epitaxial layers of a silicon supported by abase semiconductor structure, as well as other semiconductor structureswell known to one skilled in the art. Furthermore, when reference ismade to a semiconductor in the following description, previous processsteps may have been utilized to form regions/junctions in the basesemiconductor structure, and the term semiconductor can include theunderlying layers containing such regions/junctions.

The term “conductive” as used herein, as well as its various relatedforms, e.g., conduct, conductively, conducting, conduction,conductivity, etc., refers to electrically conductive unless otherwiseapparent from the context. Similarly, the term “connecting” as usedherein, as well as its various related forms, e.g., connect, connected,connection, etc., refers to electrically connecting unless otherwiseapparent from the context.

FIG. 1 is a simplified block diagram of a first apparatus (e.g., anintegrated circuit device), in the form of a memory (e.g., memorydevice) 100, in communication with a second apparatus, in the form of aprocessor 130, as part of a third apparatus, in the form of anelectronic system, according to an embodiment. Some examples ofelectronic systems include personal computers, personal digitalassistants (PDAs), digital cameras, digital media players, digitalrecorders, games, appliances, vehicles, wireless devices, cellulartelephones and the like. The processor 130, e.g., a controller externalto the memory device 100, may be a memory controller or other externalhost device.

Memory device 100 includes an array of memory cells 104 logicallyarranged in rows and columns. Memory cells of a logical row aretypically connected to the same access line (commonly referred to as aword line) while memory cells of a logical column are typicallyselectively connected to the same data line (commonly referred to as abit line). A single access line may be associated with more than onelogical row of memory cells and a single data line may be associatedwith more than one logical column. Memory cells (not shown in FIG. 1) ofat least a portion of array of memory cells 104 are capable of beingprogrammed to one of at least two data states.

A row decode circuitry 108 and a column decode circuitry 110 areprovided to decode address signals. Address signals are received anddecoded to access the array of memory cells 104. Memory device 100 alsoincludes input/output (I/O) control circuitry 112 to manage input ofcommands, addresses and data to the memory device 100 as well as outputof data and status information from the memory device 100. An addressregister 114 is in communication with I/O control circuitry 112 and rowdecode circuitry 108 and column decode circuitry 110 to latch theaddress signals prior to decoding. A command register 124 is incommunication with I/O control circuitry 112 and control logic 116 tolatch incoming commands. A trim register 128 may be in communicationwith the control logic 116 to store trim settings. Although depicted asa separate storage register, trim register 128 may represent a portionof the array of memory cells 104. Trim settings are generally valuesused by an integrated circuit device to define values of voltage levels,control signals, timing parameters, quantities, options, etc. to be usedduring operation of that integrated circuit device.

A controller (e.g., the control logic 116 internal to the memory device100) controls access to the array of memory cells 104 in response to thecommands and generates status information for the external processor130, i.e., control logic 116 is configured to perform access operations(e.g., read operations, program operations and/or erase operations) andother operations in accordance with embodiments described herein. Thecontrol logic 116 is in communication with row decode circuitry 108 andcolumn decode circuitry 110 to control the row decode circuitry 108 andcolumn decode circuitry 110 in response to the addresses.

Control logic 116 may also be in communication with a cache register118. Cache register 118 may latch data, either incoming or outgoing, asdirected by control logic 116 to temporarily store data while the arrayof memory cells 104 is busy writing or reading, respectively, otherdata. During a program operation (e.g., write operation), data may bepassed from the cache register 118 to data register 120 for transfer tothe array of memory cells 104; then new data may be latched in the cacheregister 118 from the I/O control circuitry 112. During a readoperation, data may be passed from the cache register 118 to the I/Ocontrol circuitry 112 for output to the external processor 130; then newdata may be passed from the data register 120 to the cache register 118.The cache register 118 and/or the data register 120 may form (e.g., mayform a portion of) a page buffer of the memory device 100. A page buffermay further include sensing devices (not shown) to sense a data state ofa memory cell of the array of memory cells 104. A status register 122 isin communication with I/O control circuitry 112 and control logic 116 tolatch the status information for output to the processor 130.

Memory device 100 receives control signals at control logic 116 fromprocessor 130 over a control link 132. The control signals might includea chip enable CE#, a command latch enable CLE, an address latch enableALE, a write enable WE#, a read enable RE#, and a write protect WP#.Additional or alternative control signals (not shown) may be furtherreceived over control link 132 depending upon the nature of the memorydevice 100. Memory device 100 receives command signals (which representcommands), address signals (which represent addresses), and data signals(which represent data) from processor 130 over a multiplexedinput/output (I/O) bus 134 and outputs data to processor 130 over I/Obus 134.

For example, the commands may be received over input/output (I/O) pins[7:0] of I/O bus 134 at I/O control circuitry 112 and may be writteninto command register 124. The addresses may be received overinput/output (I/O) pins [7:0] of I/O bus 134 at I/O control circuitry112 and may be written into address register 114. The data may bereceived over input/output (I/O) pins [7:0] for an 8-bit device orinput/output (I/O) pins [15:0] for a 16-bit device at I/O controlcircuitry 112 and may be written into cache register 118. The data maybe subsequently written into data register 120 for programming the arrayof memory cells 104. For another embodiment, cache register 118 may beomitted, and the data may be written directly into data register 120.Data may also be output over input/output (I/O) pins [7:0] for an 8-bitdevice or input/output (I/O) pins [15:0] for a 16-bit device. The I/Obus 134 might further include complementary data strobes DQS and DQSNthat may provide a synchronous reference for data input and output.Although reference may be made to I/O pins, they may include anyconductive node providing for electrical connection to the memory device100 by an external device (e.g., processor 130), such as conductive padsor conductive bumps as are commonly used.

It will be appreciated by those skilled in the art that additionalcircuitry and signals can be provided, and that the memory device 100 ofFIG. 1 has been simplified. It should be recognized that thefunctionality of the various block components described with referenceto FIG. 1 may not necessarily be segregated to distinct components orcomponent portions of an integrated circuit device. For example, asingle component or component portion of an integrated circuit devicecould be adapted to perform the functionality of more than one blockcomponent of FIG. 1. Alternatively, one or more components or componentportions of an integrated circuit device could be combined to performthe functionality of a single block component of FIG. 1.

Additionally, while specific I/O pins are described in accordance withpopular conventions for receipt and output of the various signals, it isnoted that other combinations or numbers of I/O pins may be used in thevarious embodiments.

FIG. 2A is a schematic of a portion of an array of memory cells 200A ascould be used in a memory of the type described with reference to FIG.1, e.g., as a portion of array of memory cells 104. Memory array 200Aincludes access lines, such as word lines 202 ₀ to 202 _(N), and datalines, such as bit lines 204 ₀ to 204 _(M). The word lines 202 may beconnected to global access lines (e.g., global word lines), not shown inFIG. 2A, in a many-to-one relationship. For some embodiments, memoryarray 200A may be formed over a semiconductor that, for example, may beconductively doped to have a conductivity type, such as a p-typeconductivity, e.g., to form a p-well, or an n-type conductivity, e.g.,to form an n-well.

Memory array 200A might be arranged in rows (each corresponding to aword line 202) and columns (each corresponding to a bit line 204). Eachcolumn may include a string of series-connected memory cells (e.g.,non-volatile memory cells), such as one of NAND strings 206 ₀ to 206_(M). Each NAND string 206 might be connected (e.g., selectivelyconnected) to a common source (SRC) 216 and might include memory cells208 ₀ to 208 _(N). The memory cells 208 may represent non-volatilememory cells for storage of data. The memory cells 208 of each NANDstring 206 might be connected in series between a select gate 210 (e.g.,a field-effect transistor), such as one of the select gates 210 ₀ to 210_(M) (e.g., that may be source select transistors, commonly referred toas select gate source), and a select gate 212 (e.g., a field-effecttransistor), such as one of the select gates 212 ₀ to 212 _(M) (e.g.,that may be drain select transistors, commonly referred to as selectgate drain). Select gates 210 ₀ to 210 _(M) might be commonly connectedto a select line 214, such as a source select line (SGS), and selectgates 212 ₀ to 212 _(M) might be commonly connected to a select line215, such as a drain select line (SGD). Although depicted as traditionalfield-effect transistors, the select gates 210 and 212 may utilize astructure similar to (e.g., the same as) the memory cells 208. Theselect gates 210 and 212 might represent a plurality of select gatesconnected in series, with each select gate in series configured toreceive a same or independent control signal.

A source of each select gate 210 might be connected to common source216. The drain of each select gate 210 might be connected to a memorycell 208 ₀ of the corresponding NAND string 206. For example, the drainof select gate 210 ₀ might be connected to memory cell 208 ₀ of thecorresponding NAND string 206 ₀. Therefore, each select gate 210 mightbe configured to selectively connect a corresponding NAND string 206 tocommon source 216. A control gate of each select gate 210 might beconnected to select line 214.

The drain of each select gate 212 might be connected to the bit line 204for the corresponding NAND string 206. For example, the drain of selectgate 212 ₀ might be connected to the bit line 204 ₀ for thecorresponding NAND string 206 ₀. The source of each select gate 212might be connected to a memory cell 208 _(N) of the corresponding NANDstring 206. For example, the source of select gate 212 ₀ might beconnected to memory cell 208 _(N) of the corresponding NAND string 206₀. Therefore, each select gate 212 might be configured to selectivelyconnect a corresponding NAND string 206 to the corresponding bit line204. A control gate of each select gate 212 might be connected to selectline 215.

The memory array in FIG. 2A might be a three-dimensional memory array,e.g., where NAND strings 206 may extend substantially perpendicular to aplane containing the common source 216 and to a plane containing aplurality of bit lines 204 that may be substantially parallel to theplane containing the common source 216.

Typical construction of memory cells 208 includes a data-storagestructure 234 (e.g., a floating gate, charge trap, etc.) that candetermine a data state of the memory cell (e.g., through changes inthreshold voltage), and a control gate 236, as shown in FIG. 2A. Thedata-storage structure 234 may include both conductive and dielectricstructures while the control gate 236 is generally formed of one or moreconductive materials. In some cases, memory cells 208 may further have adefined source/drain (e.g., source) 230 and a defined source/drain(e.g., drain) 232. Memory cells 208 have their control gates 236connected to (and in some cases form) a word line 202.

A column of the memory cells 208 may be a NAND string 206 or a pluralityof NAND strings 206 selectively connected to a given bit line 204. A rowof the memory cells 208 may be memory cells 208 commonly connected to agiven word line 202. A row of memory cells 208 can, but need not,include all memory cells 208 commonly connected to a given word line202. Rows of memory cells 208 may often be divided into one or moregroups of physical pages of memory cells 208, and physical pages ofmemory cells 208 often include every other memory cell 208 commonlyconnected to a given word line 202. For example, memory cells 208commonly connected to word line 202 _(N) and selectively connected toeven bit lines 204 (e.g., bit lines 204 ₀, 204 ₂, 204 ₄, etc.) may beone physical page of memory cells 208 (e.g., even memory cells) whilememory cells 208 commonly connected to word line 202 _(N) andselectively connected to odd bit lines 204 (e.g., bit lines 204 ₁, 204₃, 204 ₅, etc.) may be another physical page of memory cells 208 (e.g.,odd memory cells). Although bit lines 204 ₃-204 ₅ are not explicitlydepicted in FIG. 2A, it is apparent from the figure that the bit lines204 of the array of memory cells 200A may be numbered consecutively frombit line 204 ₀ to bit line 204 _(M). Other groupings of memory cells 208commonly connected to a given word line 202 may also define a physicalpage of memory cells 208. For certain memory devices, all memory cellscommonly connected to a given word line might be deemed a physical pageof memory cells. The portion of a physical page of memory cells (which,in some embodiments, could still be the entire row) that is read duringa single read operation or programmed during a single programmingoperation (e.g., an upper or lower page of memory cells) might be deemeda logical page of memory cells. A block of memory cells may includethose memory cells that are configured to be erased together, such asall memory cells connected to word lines 202 ₀-202 _(N) (e.g., all NANDstrings 206 sharing common word lines 202). Unless expresslydistinguished, a reference to a page of memory cells herein refers tothe memory cells of a logical page of memory cells.

FIG. 2B is another schematic of a portion of an array of memory cells200B as could be used in a memory of the type described with referenceto FIG. 1, e.g., as a portion of array of memory cells 104. Likenumbered elements in FIG. 2B correspond to the description as providedwith respect to FIG. 2A. FIG. 2B provides additional detail of oneexample of a three-dimensional NAND memory array structure. Thethree-dimensional NAND memory array 200B may incorporate verticalstructures which may include semiconductor pillars where a portion of apillar may act as a channel region of the memory cells of NAND strings206. The NAND strings 206 may be each selectively connected to a bitline 204 ₀-204 _(M) by a select transistor 212 (e.g., that may be drainselect transistors, commonly referred to as select gate drain) and to acommon source 216 by a select transistor 210 (e.g., that may be sourceselect transistors, commonly referred to as select gate source).Multiple NAND strings 206 might be selectively connected to the same bitline 204. Subsets of NAND strings 206 can be connected to theirrespective bit lines 204 by biasing the select lines 215 ₀-215 _(K) toselectively activate particular select transistors 212 each between aNAND string 206 and a bit line 204. The select transistors 210 can beactivated by biasing the select line 214. Each word line 202 may beconnected to multiple rows of memory cells of the memory array 200B.Rows of memory cells that are commonly connected to each other by aparticular word line 202 may collectively be referred to as tiers.

FIG. 3 is a schematic illustrating circuitry for selective connection ofa data line, for an array of memory cells as could be used in a memoryof the type described with reference to FIG. 1, to a source or othercircuitry of the memory. In particular, FIG. 3 depicts the selectiveconnection of a data line 204′ to a source (e.g., common source) 216through a transistor (e.g., an n-type field-effect transistor or nFET)311, and the selective connection of the data line 204′ to a node 319through a transistor (e.g., an nFET) 315. The node 319 might provideconnection to peripheral circuitry of an array of memory cells. Forexample, the node 319 might provide connection to a page buffer, e.g.,the cache register 118 and/or data register 120 of FIG. 1. The data line204′ might represent any data line 204 of FIG. 2A or 2B, while thesource 216 might represent the source 216 of FIG. 2A or 2B, for example.

The transistor 311 might selectively connect the data line 204′ to thesource 26 in response to a control signal from control signal node 313applied to the control gate of the transistor 311. The control signalnode 313 may be connected to a control gate for each of a number oftransistors 311 connected between other data lines 204 and the source216. The data line 204′ might be connected to the source 216 during anerase operation, while being isolated from the node 319. The transistor315 might selectively connect the data line 204′ to the node 319 inresponse to a control signal from control signal node 317 applied to thecontrol gate of the transistor 315. The data line 204′ might beconnected to the node 319 during a read operation or a programmingoperation, while being isolated from the source 216.

Typically, an erase operation includes a series of erase pulses appliedto the NAND strings 206 through their respective data lines 204 andsource 216 while voltage levels are applied to the access lines 202sufficient to activate the corresponding memory cells. An erase verifyoperation may be performed between pulses to determine if the memorycells have been sufficiently erased (e.g., have threshold voltages at orbelow some target value). If the erase verify is failed, another erasepulse, typically having a higher voltage level, may be applied. For eachpulse, the transistor 311 might be activated in response to a rampedvoltage signal on the control signal node 313, e.g., a ramp from 0V tothe voltage level above the voltage level the erase pulse (e.g., 24V),while a voltage of the source 216 and the data line 204′ areconcurrently ramped up, e.g., a ramp from 0V to the voltage level of theerase pulse (e.g., 20V) for this example. As used herein, a first actand a second act occur concurrently when the first act occurssimultaneously with the second act for at least a portion of a durationof the second act. For example, for at least a portion of ramping up thevoltage level of the data line and the source, the voltage level of thecontrol gate of the transistor 311 is being simultaneously ramped up.

Ramping of such voltages can be generally well controlled by voltagegeneration devices (not shown) of a memory device. Following the erasepulse, these voltages are generally discharged to prepare for an eraseverify or other subsequent access operation. The voltage level on thecontrol signal node 313 might be allowed to electrically float while thevoltage level of the data line 204′ is discharged, with an expectationthat the voltage level of the control signal node 313 might follow thevoltage level of the data line 204′ due to gate-drain coupling. Forexample, the control signal node 313 might be electrically isolated fromany voltage supply, such that voltage discharge may be the result ofcapacitive coupling between the control signal node 313 and the dataline 204′. However, depending upon the degree of coupling and otherfactors, variations beyond desired operating conditions might develop.For example, the voltage level of the control signal node 313 maydischarge too slowly, and a voltage difference across the transistor 311might exceed a breakdown voltage of that device. Various embodimentsseek to mitigate such variations by providing control of the dischargeof the control signal node 313, e.g., the voltage level to the controlgate of the transistor 311.

FIG. 4 is a block schematic of circuitry for selectively controllingdischarge of a control gate voltage in accordance with an embodiment.The circuitry of FIG. 4 might include a comparator (e.g., a differentialamplifier) 421 ₀ having a first input (e.g., an inverting or “−” input)connected to a voltage node 423 ₀. The voltage node 423 ₀ may becapacitively coupled to the data line 204′ through a capacitance (e.g.,capacitor) 427 ₀. The capacitance 427 ₀ may be connected (e.g.,selectively connected) to the data line 204′. The capacitance 427 ₀ mayrepresent one or more capacitors connected in parallel and/or series toprovide a particular capacitance value C₀₀. The voltage node 423 ₀ maybe further capacitively coupled to a reference node 435 ₀ through acapacitance (e.g., capacitor) 429 ₀. The reference node 435 ₀ might becoupled to receive a reference potential, such as a ground potential Vssor 0V. The capacitance 429 ₀ may represent one or more capacitorsconnected in parallel and/or series to provide a particular capacitanceC₁₀. The sizing and ratio of the capacitance values C₀₀ and C₁₀ might bechosen to divide the voltage level of the data line 204′ down to a value(e.g., expected range of values) at the voltage node 423 ₀ that issuitable for operation of the comparator 421 ₀.

The voltage node 423 ₀ may further be selectively connected to a voltagenode 447 ₀ through a transistor (e.g., an nFET) 445 ₀ responsive to acontrol signal from control signal node 449 ₀ connected to the controlgate of the transistor 445 ₀. The voltage node 447 ₀ may be configuredto receive a reference voltage Vrefinit0 that might represent a firstthreshold, e.g., a high limit. Use and determination of the referencevoltage Vrefinit0 will be described infra.

The comparator 421 ₀ might have a second input (e.g., a non-inverting or“+” input) connected to a voltage node 425 ₀. The comparator 421 ₀ maybe configured to provide a first logic level, e.g., a logic high level,if the voltage level at its second input is less than the voltage levelat its first input, and a second logic level, e.g., a logic low level,if the voltage level at its second input is greater than the voltagelevel at its first input. The voltage node 425 ₀ may be capacitivelycoupled to the control signal node 313, and thus to a voltage level ofthe control gate of the transistor connected between the data line 204′and the source 216, through a capacitance (e.g., capacitor) 431 ₀. Thecapacitance 431 ₀ may be connected (e.g., selectively connected) to thecontrol signal node. The capacitance 431 ₀ may represent one or morecapacitors connected in parallel and/or series to provide a particularcapacitance value C₂₀. The voltage node 425 ₀ may be furthercapacitively coupled to a reference node 435 ₁ through a capacitance(e.g., capacitor) 433 ₀. The reference node 435 ₁ might be coupled toreceive a reference potential, such as a ground potential Vss or 0V. Thereference node 435 ₁ may be a same voltage node as the reference node435 ₀. The capacitance 433 ₀ may represent one or more capacitorsconnected in parallel and/or series to provide a particular capacitanceC₃₀. The sizing and ratio of the capacitance values C₂₀ and C₃₀ might bechosen to divide the voltage level of the control signal node 313 downto a value (e.g., expected range of values) at the voltage node 425 ₀that is suitable for operation of the comparator 421 ₀. The sizing andratio of the capacitance values C₂₀ and C₃₀ might be chosen to besubstantially equal (e.g., equal) to the sizing and ratio of thecapacitance values C₀₀ and C₁₀, respectively. The phrase “substantiallyequal” as used herein recognizes that even where values may be intendedto be equal, variabilities and accuracies of industrial processing maylead to differences from their intended values. These variabilities andaccuracies will generally be dependent upon the technology utilized infabrication of the integrated circuit device.

The circuitry of FIG. 4 might further include a comparator (e.g., adifferential amplifier) 421 ₁ having a first input (e.g., an invertingor “−” input) connected to a voltage node 425 ₁. The voltage node 425 ₁may be capacitively coupled to the control signal node 313, and thus toa voltage level of the control gate of the transistor connected betweenthe data line 204′ and the source 216, through a capacitance (e.g.,capacitor) 431 ₁. The capacitance 431 ₁ may be connected (e.g.,selectively connected) to the control signal node 313. The capacitance431 ₁ may represent one or more capacitors connected in parallel and/orseries to provide a particular capacitance value C₂₁. The voltage node425 ₁ may be further capacitively coupled to a reference node 435 ₃through a capacitance (e.g., capacitor) 433 ₁. The reference node 435 ₃might be coupled to receive a reference potential, such as a groundpotential Vss or 0V. The capacitance 433 ₁ may represent one or morecapacitors connected in parallel and/or series to provide a particularcapacitance C₃₁. The sizing and ratio of the capacitance values C₂₁ andC₃₁ might be chosen to divide the voltage level of the control signalnode 313 down to a value (e.g., expected range of values) at the voltagenode 425 ₁ that is suitable for operation of the comparator 421 ₁.

The comparator 421 ₁ might have a second input (e.g., a non-inverting or“+” input) connected to a voltage node 423 ₁. The comparator 421 ₁ maybe configured to provide a first logic level, e.g., a logic high level,if the voltage level at its second input is less than the voltage levelat its first input, and a second logic level, e.g., a logic low level,if the voltage level at its second input is greater than the voltagelevel at its first input. The voltage node 423 ₁ may be capacitivelycoupled to the data line 204′ through a capacitance (e.g., capacitor)427 ₁. The capacitance 427 ₁ may be connected (e.g., selectivelyconnected) to the data line 204′. The capacitance 427 ₁ may representone or more capacitors connected in parallel and/or series to provide aparticular capacitance value Col. The voltage node 423 ₁ may be furthercapacitively coupled to a reference node 435 ₂ through a capacitance(e.g., capacitor) 429 ₁. The reference node 435 ₂ might be coupled toreceive a reference potential, such as a ground potential Vss or 0V. Thereference node 435 ₂ may be a same voltage node as the reference node435 ₃, and may further be a same voltage node as the reference nodes 435₀ and 435 ₁. The capacitance 429 ₁ may represent one or more capacitorsconnected in parallel and/or series to provide a particular capacitanceC₁₁. The sizing and ratio of the capacitance values C₀₁ and C₁₁ might bechosen to divide the voltage level of the data line 204′ down to a value(e.g., expected range of values) at the voltage node 423 ₁ that issuitable for operation of the comparator 421 ₁. The sizing and ratio ofthe capacitance values C₀₁ and C₁₁ might be chosen to be substantiallyequal (e.g., equal) to the sizing and ratio of the capacitance valuesC₂₁ and C₃₁, respectively.

The voltage node 423 ₁ may further be selectively connected to a voltagenode 447 ₁ through a transistor (e.g., an nFET) 445 ₁ responsive to acontrol signal from control signal node 449 ₁ connected to the controlgate of the transistor 445 ₁. The voltage node 447 ₁ may be configuredto receive a reference voltage Vrefinit1 that might represent a secondthreshold, e.g., a low limit. Use and determination of the referencevoltage Vrefinit1 will be described infra. The control signal nodes 449₀ and 449 ₁ may be configured to receive a same control signal.

An output of the comparator 421 ₀ and an output of the comparator 421 ₁may be connected to logic 437. The logic 437 may be any configuration ofcombinational and/or combinatorial logic to provide an output from logic437 having a first logic level, e.g., a logic high level, if thecomparator 421 ₀ indicates that the voltage level of the voltage node425 ₀ is greater than the voltage level of the voltage node 423 ₀, andto provide an output from logic 437 having a second logic level, e.g., alogic low level, if the comparator 421 ₁ indicates that the voltagelevel of the voltage node 425 ₁ is less than the voltage level of thevoltage node 423 ₁. Note that while the first and second logic levels ofthe comparators 421 were also described in example as corresponding tothe logic high level and the logic low level, respectively, thecorrespondence of particular logic levels for the outputs of thecomparators 421 and the logic 437 may be altered while achieving thesame results.

The logic 437 might further be configured to maintain the logic level ofits output if the comparator 421 ₀ indicates that the voltage level ofthe voltage node 425 ₀ is less than the voltage level of the voltagenode 423 ₀, and the comparator 421 ₁ indicates that the voltage level ofthe voltage node 425 ₁ is greater than the voltage level of the voltagenode 423 ₁. For example, if the logic level of the output of the logic437 is the first logic level due to an output of the comparator 421 ₀indicating that the voltage level of the voltage node 425 ₀ is greaterthan the voltage level of the voltage node 423 ₀, and a logic level ofthe output of the comparator 421 ₀ transitions, the logic 437 maymaintain its output logic level at the first logic level until thecomparator 421 ₁ indicates that the voltage level of the voltage node425 ₁ is less than the voltage level of the voltage node 423 ₁.Conversely, if the logic level of the output of the logic 437 is thesecond logic level due to an output of the comparator 421 ₁ indicatingthat the voltage level of the voltage node 425 ₁ is less than thevoltage level of the voltage node 423 ₁, and a logic level of the outputof the comparator 421 ₁ transitions, the logic 437 may maintain itsoutput logic level at the second logic level until the comparator 421 ₀indicates that the voltage level of the voltage node 425 ₀ is greaterthan the voltage level of the voltage node 423 ₀. Table 1 mightrepresent a truth table for logic 437 for such an embodiment.

TABLE 1 Comparator 421₀ Comparator 421₁ Logic 437 Logic 437 OutputOutput Prior Output Current Output L H X H H H H H H H L L H L X L L =logic low; H = logic high; X = do not care

The control signal node 313 may be selectively connected to the source216 through a transistor (e.g., nFET) 441 responsive to the output ofthe logic 437. The voltage levels corresponding to one or more of thelogic levels (e.g., the logic high level) of the output of the logic 437may need to be transitioned to another voltage domain in order toprovide an appropriate control gate voltage to control the transistor441. Accordingly, a level shifter 439 may be included to transition thevoltage levels of the logic 437 to an appropriate voltage domain. Adiode-connected transistor (e.g., nFET) 443 may be included between thecontrol signal node 313 and the transistor 441. The diode-connectedtransistor 443 might be used to mitigate a risk of discharging thecontrol signal node 313 to a point where the control gate voltage of thetransistor 311 falls below its threshold voltage Vt during discharge ofthe voltage levels of the data line 204′ and the source 216.

Through selection of particular voltage levels of the reference voltagesVrefinit0 and Vrefinit1, the comparator 421 ₀ can indicate whether thevoltage level of the node 425 ₀ indicates that the voltage level of thecontrol signal node 313 is greater than an upper limit, e.g., somevoltage level in excess of the voltage level of the data line 204′ thatis less than a break-down voltage of the transistor 311 of FIG. 3, whilethe comparator 421 ₁ can indicate whether the voltage level of the node425 ₁ indicates that the voltage level of the control signal node 313 isless than a lower limit, e.g., some voltage level in excess of thevoltage level of the data line 204′ that is greater than a thresholdvoltage of the transistor 311 of FIG. 3.

To determine values of Vrefinit0 and Vrefinit1, the following equationsmay apply:

−(Vsrcinit−Vrefinit)*C1+Vrefinit*C2=−(Vsrc−Vdet_src)*C1+Vdet_src*C2  Eq.1

Vdet_src=(C1/(C1+C2))*(Vsrc−Vsrcinit)+Vrefinit  Eq. 2

Vdet_src=Vdet_hviso  Eq. 3

Vhviso−Vsrc=Vhvisoinit−Vsrcinit+((C1+C2)/C1)*(Vrefinit−Vrefhviso)  Eq. 4

Table 2 may provide definitions of the variables of the Equations 1-4.In Table 2, the voltage node 423 may correspond to the voltage node 423₀ or 423 ₁; the voltage node 425 may correspond to the voltage node 425₀ or 425 ₁, respectively; the reference node 435 may correspond to thereference node 435 ₀ or 435 ₁, respectively; Vrefinit may correspond tothe reference voltage Vrefinit0 or Vrefinit1, respectively; C1 maycorrespond to the capacitance value C₀₀ or C₀₁, respectively; and C2 maycorrespond to the capacitance value C₁₀ or C₁₁, respectively.

TABLE 2 Variable or Constant Name Definition Vsrcinit Voltage level ofthe data line 204′ prior to discharge Vsrc Voltage level of the dataline 204′ during discharge Vrefinit Voltage level of voltage node 423prior to discharge of Vsrc Vdet_src Voltage level of voltage node 423during discharge of the data line 204′ Vhvisoinit Voltage level ofcontrol signal node 313 prior to discharge Vhviso Voltage level of thecontrol signal node 313 during discharge Vrefhviso Voltage level ofvoltage node 425 prior to discharge of the control signal node 313Vdet_hviso Voltage level of voltage node 425 during discharge of thecontrol signal node 313 C1 Capacitance value of the capacitance betweenthe data line 204′ and the voltage node 423 C2 Capacitance value of thecapacitance between the voltage node 423 and the reference node 435

With reference to Equations 1-4 and Table 2, Equation 1 describes arelationship between the voltage level of the data line 204′ and thevoltage level of the voltage node 423 prior to and during discharge ofthe voltage level of the data line 204′. Equation 2 simplifies theequality of Equation 1. Equation 3 represents a condition at which thecomparator would transition under ideal conditions. Equation 4 thenrepresents the resulting relationship between the voltage level of thedata line 204′ and the voltage level of the control signal node 313prior to and during discharge of these voltage levels.

By selecting desired values for the quantity Vhviso−Vsrc, e.g., somevalue below a breakdown voltage of the transistor between the data line204′ and the source 216 and some value above a threshold voltage of thattransistor, Vrefinit0 and Vrefinit1, respectively, might be calculatedbased on known values of C1, C2, Vhvisoinit, Vsrcinit and Vrefhviso. Asan example, if the breakdown voltage of the transistor 311 of FIG. 3 is4V, Vhviso−Vsrc might be set to equal 3V. For an erase operation whereVhvisoinit=24V and Vsrcinit=22V, and for a configuration havingcapacitance values such that (C1+C2)/C1=20 producing Vrefhviso=1.00V,Vrefinit might be calculated to equal 1.05V. Accordingly, the voltagenode 447 ₀ might be configured to receive a voltage level of 1.05V asVrefinit0 to facilitate operation of the comparator 421 ₀ to indicatewhether the voltage level of the control signal node 313 is deemed to begreater than 3V above the voltage level of the data line 204′.

Continuing with this example, if the threshold voltage of the transistor311 of FIG. 3 is 1.5V, Vhviso−Vsrc might be set to equal 2V, andVrefinit might be calculated to equal 1.00V. Accordingly, the voltagenode 447 ₁ might be configured to receive a voltage level of 1.00V asVrefinit1 to facilitate operation of the comparator 421 ₁ to indicatewhether the voltage level of the control signal node 313 is deemed to beless than 2V above the voltage level of the data line 204′. Trim valuesindicative of the desired values of Vrefinit0 and Vrefinit1 might bestored to the trim register 128 of FIG. 1. As is known, trim values maybe utilized to control an output voltage level of a voltage generationdevice (not shown), such as a charge pump. For various embodiments, thetrim values may be utilized across the entire array of memory cells, ordifferent portions of the array of memory cells, such as differentblocks or even different data lines 204′, may have different trim valuesindicative of differing values of Vrefinit0 and/or Vrefinit1, e.g.,where characterization of the memory device may indicate differentoperating characteristics of the corresponding transistors 311,different initial voltage levels, or different capacitance values, etc.

FIG. 5 is a timing diagram for use in describing operation of thecircuitry of FIG. 4 in accordance with an embodiment. FIG. 5 will firstbe discussed with reference specifically to the comparator 421 ₀, andthen its application to the comparator 421 ₁ will be discussed. In FIG.5, the trace 551 may represent a voltage level of the voltage node 447₀, the trace 553 may represent a voltage level of the voltage node 423₀, and the trace 555 may represent a voltage level of the voltage node425 ₀. For this example, the transistor 445 ₀ may be activated at timet0 of FIG. 5.

Comparators, such as comparator 421 ₀, may experience offsets such thattheir output transitions at some point other than the ideal situationwhere both inputs are receiving an equal voltage level. Compensationschemes are known, and might include applying a same voltage level toboth inputs, and then adding or removing charge from one input until theoutput of the comparator transitions. With reference to FIG. 5, theperiod from time t0 to t1 might represent such a compensation scheme.For example, at time t0, Vrefinit may be applied to the voltage node 447₀, and thus the voltage node 423 ₀, at a voltage level equal to thevoltage level of Vdet_hviso of the voltage node 425 ₀. Charge might thenbe added to the voltage node 425 ₀, for example, to cause the output ofthe comparator 421 ₀ to transition. Adding charge might thus result inan increase of the voltage level of the voltage node 425 ₀ as shown. Thevoltage node 425 ₀ might then be allowed to electrically float. For someembodiments, such compensation is not performed.

At time t1, the voltage level applied to the voltage node 447 ₀ might beset (e.g., increased) to the determined value of Vrefinit0, resulting ina corresponding increase in the voltage level of the voltage node 423 ₀.At time t2, the transistor 445 ₀ may be deactivated, thus allowing thevoltage node 423 ₀ to electrically float. Discharge of the voltage levelof the data line 204′, and resulting discharge of the voltage level ofthe control signal node 313 (e.g., the voltage level of the control gateof the transistor 311), might begin at time t3. The comparator 421 ₀ maythen indicate whether the voltage level of the voltage node 425 ₀ isgreater than the voltage level of the voltage node 423 ₀. In otherwords, the comparator 421 ₀ may provide an indication whether adifference between the voltage level of the control signal node 313 andthe voltage level of the data line 204′ is deemed to be greater thansome value, e.g., some upper limit.

Referring again to FIG. 5, the trace 551 may represent a voltage levelof the voltage node 447 ₁, the trace 553 may represent a voltage levelof the voltage node 423 ₁, and the trace 555 may represent a voltagelevel of the voltage node 425 ₁. For this example, the transistor 445 ₁may be activated at time t0 of FIG. 5.

At time t0, Vrefinit may be applied to the voltage node 447 ₁, and thusthe voltage node 423 ₁, at a voltage level equal to the voltage level ofVdet_hviso of the voltage node 425 ₁. Charge might then be added to thevoltage node 425 ₁, for example, to cause the output of the comparator421 ₁ to transition. Adding charge might thus result in an increase ofthe voltage level of the voltage node 425 ₁ as shown. The voltage node425 ₁ might then be allowed to electrically float. For some embodiments,such compensation is not performed.

At time t1, the voltage level applied to the voltage node 447 ₁ might beset (e.g., increased) to the determined value of Vrefinit1, resulting ina corresponding increase in the voltage level of the voltage node 423 ₁.At time t2, the transistor 445 ₁ may be deactivated, thus allowing thevoltage node 423 ₁ to electrically float. Discharge of the voltage levelof the data line 204′, and resulting discharge of the voltage level ofthe control signal node 313 (e.g., the voltage level of the control gateof the transistor 311), might begin at time t3. The comparator 421 ₁ maythen indicate whether the voltage level of the voltage node 425 ₀ isless than the voltage level of the voltage node 423 ₁. In other words,the comparator 421 ₁ may provide an indication whether a differencebetween the voltage level of the control signal node 313 and the voltagelevel of the data line 204′ is deemed to be less than some value, e.g.,some lower limit.

FIG. 6 is a flowchart of a method of operating a memory in accordancewith an embodiment. The method of FIG. 6 might occur during an eraseoperation, e.g., during the discharge of the erase voltages from thedata line 204′ and the source 216 following an erase pulse. The methodmay be performed for each of a number of data lines 204′, e.g., eachdata line of memory cells subjected to the erase voltages, and may beperformed concurrently for each of these data lines. This might be trueregardless of whether each of those memory cells were selected for eraseduring the erase operation, e.g., where multiple blocks of memory cellsshare a common source 216, but may be erased individually.

At 661, a voltage level of a data line and a voltage level of a sourceare discharged concurrently. Discharge of the voltage level of the dataline may include discharging the data line to the source through atransistor connected therebetween, e.g., transistor 311 of FIG. 3. At663, a representation of a voltage difference between a voltage level ofthe data line and a voltage level of a control gate of a transistorconnected between the data line and the source is monitored, e.g.,concurrently with discharging the voltage level of the data line. If thevoltage difference is deemed to be greater than a first value, a currentpath between the control gate of the transistor and the source may beactivated at 665. For example, the control gate of the transistor andthe source might be electrically connected. If the voltage difference isdeemed to be less than a second value, the current path between thecontrol gate of the transistor and the source may be deactivated at 667.For example, the control gate of the transistor and the source might beelectrically isolated. The second value may be less than the firstvalue, e.g., the second value may correspond to a voltage differencethat is less than a voltage difference corresponding to the first value.

FIG. 7 is a flowchart of a method of operating a memory in accordancewith an embodiment. The method of FIG. 7 might occur during an eraseoperation, e.g., during the discharge of the erase voltages from thedata line 204′ and the source 216 following an erase pulse. The methodmay be performed for each of a number of data lines 204′, e.g., eachdata line of memory cells subjected to the erase voltages, and may beperformed concurrently for each of these data lines. This might be trueregardless of whether each of those memory cells were selected for eraseduring the erase operation, e.g., where multiple blocks of memory cellsshare a common source 216, but may be erased individually.

At 780, a first particular voltage level (e.g., Vrefinit0) is applied toa first voltage node (e.g., voltage node 423 ₀) capacitively coupled toa voltage level of a data line (e.g., data line 204′), then the firstvoltage node is allowed to electrically float (e.g., is electricallyfloated). At 782, a second particular voltage level (e.g., Vrefinit1) isapplied to a second voltage node (e.g., voltage node 423 ₁) capacitivelycoupled to the voltage level of the data line (e.g., data line 204′),then the second voltage node is allowed to electrically float (e.g., iselectrically floated). The application of the second particular voltagelevel at 782 may be performed prior to 780, concurrently with 780 orsubsequent to 780.

At 784, e.g., while the first voltage node and the second voltage nodeare electrically floating, the voltage level of the data line and thevoltage level of a source (e.g., source 216) are concurrentlydischarged.

At 786, e.g., while discharging the voltage level of the data line andthe voltage level of the source, a voltage level of the first voltagenode is compared to a voltage level of a third voltage node (e.g.,voltage node 425 ₀) capacitively coupled to a voltage level (e.g., ofcontrol signal node 313) of a control gate of a transistor (e.g.,transistor 311) connected between the data line and the source. At 788,e.g., while discharging the voltage level of the data line and thevoltage level of the source, a voltage level of the second voltage nodeis compared to a voltage level of a fourth voltage node (e.g., voltagenode 425 ₁) capacitively coupled to a voltage level (e.g., of controlsignal node 313) of the control gate of the transistor connected betweenthe data line and the source.

At 790, e.g., while discharging the voltage level of the data line andthe voltage level of the source, a current path (e.g., transistor 441)between the source and the control gate of the transistor connectedbetween the data line and the source may be activated while the voltagelevel of the third voltage node is deemed to be greater than the voltagelevel of the first voltage node. At 792, e.g., while discharging thevoltage level of the data line and the voltage level of the source, thecurrent path between the source and the control gate of the transistorconnected between the data line and the source may be deactivated whilethe voltage level of the fourth voltage node is deemed to be less thanthe voltage level of the second voltage node.

CONCLUSION

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe embodiments will be apparent to those of ordinary skill in the art.Accordingly, this application is intended to cover any adaptations orvariations of the embodiments.

What is claimed is:
 1. An integrated circuit device, comprising: a firstnode; a second node; a transistor connected between the first node andthe second node; a current path between a control gate of the transistorand the second node; and a controller, wherein the controller isconfigured to: concurrently discharge a voltage level of the first nodeand a voltage level of the second node; monitor a representation of avoltage difference between the voltage level of the first node and avoltage level of the control gate of the transistor while dischargingthe voltage level of the first node and discharging the voltage level ofthe second node; activate the current path if the voltage difference isdeemed to be greater than a first value; and deactivate the current pathif the voltage difference is deemed to be less than a second value. 2.The integrated circuit device of claim 1, wherein the controller beingconfigured to monitor the representation of the voltage differencebetween the voltage level of the first node and the voltage level of thecontrol gate of the transistor comprises the controller being configuredto: monitor an output of a first comparator having a first inputcapacitively coupled to the first node and a second input capacitivelycoupled to the control gate of the transistor, wherein the output of thefirst comparator is configured to indicate whether the voltagedifference is deemed to be greater than the first value; and monitor anoutput of a second comparator having a first input capacitively coupledto the control gate of the transistor and a second input capacitivelycoupled to the first node, wherein the output of the second comparatoris configured to indicate whether the voltage difference is deemed to beless than the second value.
 3. The integrated circuit device of claim 1,wherein the controller, after activating the current path if the voltagedifference is deemed to be greater than the first value, is furtherconfigured to: maintain activation of the current path if the voltagedifference is no longer deemed to be greater than the first value andthe voltage difference is deemed to be greater than the second value. 4.The integrated circuit device of claim 3, wherein the controller, afterdeactivating the current path if the voltage difference is deemed to beless than the second value, is further configured to: maintaindeactivation of the current path if the voltage difference is no longerdeemed to be less than the second value and the voltage difference isdeemed to be less than the first value.
 5. The integrated circuit deviceof claim 1, wherein the first value is selected such that the controlleris configured to activate the current path before the voltage differenceis deemed to be greater than a breakdown voltage of the transistor, andwherein the second value is selected such that the controller isconfigured to deactivate the current path before the voltage differenceis deemed to be less than a threshold voltage of the transistor.
 6. Theintegrated circuit device of claim 1, wherein the transistor is a firsttransistor, and wherein the current path comprises: a second transistorconnected between the second node and the control gate of the firsttransistor; and a third transistor connected between the secondtransistor and the control gate of the first transistor; wherein acontrol gate of the third transistor is connected to the control gate ofthe first transistor; wherein the controller is configured to activatethe current path by activating the second transistor; and wherein thecontroller is configured to deactivate the current path by deactivatingthe second transistor.
 7. An integrated circuit device, comprising: afirst node; a second node selectively connected to the first nodethrough a transistor; a first voltage node capacitively coupled to avoltage level of the first node; a second voltage node capacitivelycoupled to the voltage level of the first node; a third voltage nodecapacitively coupled to a voltage level of a control gate of thetransistor; a fourth voltage node capacitively coupled to the voltagelevel of the control gate of the transistor; a current path between thesecond node and the control gate of the transistor; and a controllerconfigured to: apply a first voltage level to the first voltage node,then allow the first voltage node to electrically float; apply a secondvoltage level, lower than the first voltage level, to the second voltagenode, then allow the second voltage node to electrically float;concurrently discharge the voltage level of the first node and a voltagelevel of the second node; compare a voltage level of the first voltagenode to a voltage level of the third voltage node; compare a voltagelevel of the second voltage node to a voltage level of the fourthvoltage node; activate the current path while the voltage level of thethird voltage node is deemed to be greater than the voltage level of thefirst voltage node; and deactivate the current path while the voltagelevel of the fourth voltage node is deemed to be less than the voltagelevel of the second voltage node.
 8. The integrated circuit device ofclaim 7, wherein the controller is configured to apply the secondvoltage level to the second voltage and to apply the first voltage levelto the first voltage node concurrently.
 9. The integrated circuit deviceof claim 7, wherein the controller being configured to discharge thevoltage level of the first node comprises the controller beingconfigured to discharge the voltage level of the first node to thesecond node through the transistor.
 10. The integrated circuit device ofclaim 7, wherein the controller is further configured to: electricallyfloat the first voltage node and electrically float the third voltagenode while comparing the voltage level of the first voltage node to thevoltage level of a third voltage node; and electrically float the secondvoltage node and electrically float the fourth voltage node whilecomparing the voltage level of the second voltage node to the voltagelevel of the fourth voltage node.
 11. The integrated circuit device ofclaim 10, wherein the controller is further configured to: adjust alevel of charge on the third voltage node prior to applying the firstvoltage level to the first voltage node, and prior to electricallyfloating the third voltage node; and adjust a level of charge on thefourth voltage node prior to applying the second voltage level to thesecond voltage node, and prior to electrically floating the fourthvoltage node.
 12. The integrated circuit device of claim 7, wherein thetransistor is a first transistor, and wherein the current pathcomprises: a second transistor between the second node and the controlgate of the transistor; wherein activating the current path comprisesactivating the second transistor; and wherein deactivating the currentpath comprises deactivating the second transistor.
 13. The integratedcircuit device of claim 7, wherein the first voltage level is selectedsuch that the voltage level of the third voltage node would be deemed tobe greater than the voltage level of the first voltage node before avoltage difference between the voltage level of the control gate of thetransistor and the voltage level of the first node exceeds a breakdownvoltage of the transistor, and wherein the second voltage level isselected such that the voltage level of the fourth voltage node would bedeemed to be less than the voltage level of the second voltage nodebefore a voltage difference between the voltage level of the controlgate of the transistor and the voltage level of the first node is lessthan a threshold voltage of the transistor.
 14. An integrated circuitdevice, comprising: a first node; a second node selectively connected tothe first node through a transistor; a first comparator having a firstinput capacitively coupled to the first node, a second inputcapacitively coupled to a control gate of the transistor, and an output;a second comparator having a first input capacitively coupled to thecontrol gate of the transistor, a second input capacitively coupled tothe first node, and an output; a first voltage node connected to thefirst input of the first comparator, and capacitively coupled to a firstreference node; a second voltage node connected to the second input ofthe second comparator, and capacitively coupled to a second referencenode; a third voltage node connected to the second input of the firstcomparator, and capacitively coupled to a third reference node; a fourthvoltage node connected to the first input of the second comparator, andcapacitively coupled to a fourth reference node; a fifth voltage nodeselectively connected to the first voltage node and configured toreceive a first reference voltage; a sixth voltage node selectivelyconnected to the second voltage node and configured to receive a secondreference voltage; a logic having a first input connected to the outputof the first comparator and a second input connected to the output ofthe second comparator, and having an output configured to provide afirst logic level when the output of the first comparator indicates thata voltage level of its second input is greater than a voltage level ofits first input, and to provide a second logic level, different from thefirst logic level, when the output of the second comparator indicatesthat a voltage level of its first input is less than a voltage level ofits second input; and a current path between the second node and thecontrol gate of the transistor, wherein the current path is configuredto be activated in response to the output of the logic having the firstlogic level, and to be deactivated in response to the output of thelogic having the second logic level.
 15. The integrated circuit deviceof claim 14, wherein the logic is further configured to maintain thefirst logic level at its output if the output of the first comparatortransitions to indicate that the voltage level of its second input is nolonger greater than the voltage level of its first input while theoutput of the second comparator indicates that the voltage level of itsfirst input is greater than the voltage level of its second input, andto maintain the second logic level at its output if the output of thesecond comparator transitions to indicate that the voltage level of itsfirst input is no longer less than the voltage level of its second inputwhile the output of the first comparator indicates that the voltagelevel of its second input is less than the voltage level of its firstinput.
 16. The integrated circuit device of claim 14, wherein the firstreference node, the second reference node, the third reference node andthe fourth reference node are each configured to receive a particularvoltage level.
 17. The integrated circuit device of claim 16, whereinthe particular voltage level is a ground potential.
 18. The integratedcircuit device of claim 14, wherein the first comparator comprises afirst differential amplifier, wherein the second comparator comprises asecond differential amplifier, wherein the first input of the firstcomparator is an inverting input of the first differential amplifier,and wherein the first input of the second comparator is an invertinginput of the second differential amplifier.
 19. The integrated circuitdevice of claim 14, wherein the transistor is a first transistor, andwherein the current path comprises a second transistor connected betweensecond node and the control gate of the first transistor, the integratedcircuit device further comprising: a level shifter configured totransition a voltage level of the output of the logic to a voltagedomain configured to activate the second transistor when the output ofthe logic has the first logic level, and to deactivate the secondtransistor when the output of the logic has the second logic level. 20.The integrated circuit device of claim 19, wherein the current pathfurther comprises a diode-connected third transistor connected betweenthe second transistor and the control gate of the first transistor, andconfigured to mitigate a risk of discharging the voltage level of thecontrol gate of the first transistor below a threshold voltage of thefirst transistor.